Automated business machines for producing or reproducing hard copy documents, such as copiers, printers, telecommunications facsimile and digital sending machines, document scanners, multi-function devices (MFD), and the like, are well-known commercially. Ideally, when working with cut sheet print media, a copying or optical scanning apparatus will provide both manual document feed and automatic document feed capabilities. Often such apparatus include an automatic document feeder (ADF) mechanism for automatically loading and unloading single sheets sequentially to a functional station where the apparatus performs an operation, e.g., sequentially scanning the fed document sheets for copying, faxing, displaying on a computer monitor, or the like. Following the operation, the ADF then off-loads a sheet and feeds the immediately following sheet of the document to the functional station. A sequential flow of sheets by the ADF and positioning without the necessity of manual handling reduces the time required to accomplish the complete functional operation.
Optical scanners operate by imaging an object (from a sheet of paper, document or other form of medium) with a light source, sensing a resultant light signal with an optical sensor array. Each optical sensor in the array generates a data signal representative of the intensity of light impinged thereon for a corresponding portion of the imaged object. The data signals from the array sensors are then processed (typically digitized) and stored in a temporary memory such as a semiconductor memory or on a hard disk of a computer, for example, for subsequent manipulation and printing or display, such as on a computer monitor. The image of the scanned object is projected onto the optical photo sensor array incrementally by use of a moving scan line. The moving scan line is produced either by moving the document with respect to the scanner optical assembly, or by moving scanner optical assembly relative to the document. Either or both of these methods may be embodied in flat bed scanners, hand held scanners, or any scanner having manual and automatic feed capabilities.
Various types of photo sensor devices may be used in optical scanners. For example, a commonly used photo sensor device is the charge coupled device (CCD). A CCD builds up an electrical charge in response to exposure to light. The size of the electrical charge build up is dependent on the intensity and the duration of the light exposure. In optical scanners, CCD cells are aligned in linear array. Each cell or “pixel” has a portion of a scan line image impinged thereon as the scan line sweeps across the scanned object. The charge built up in each of the pixels is measured and discharged at regular “sampling intervals.” In most modern optical scanners, the sampling intervals of the CCD arrays are fixed.
As previously mentioned, an image of a scan line portion of a document is projected onto the scanner's linear sensor array by scanner optics. In CCD scanners, the scanner optics include an imaging lens which typically reduces considerably the size of the projected image from the its original size. Pixels in a scanner linear photo sensor array are aligned in a “cross” direction, i.e., a direction parallel to the longitudinal axis of the scan line image which is projected thereon. The direction perpendicular to the “cross” direction will be referred to herein as the “scan” direction (i.e., paper or sensor linear array movement direction for scanning of the image).
At any instant when an object is being scanned, each pixel in the sensor array has a corresponding area on the object which is being imaged thereon. This corresponding area on the scanned object is referred to herein as an “object pixel” or simply “pixel.” An area on a scanned object corresponding in area to the entire area of the linear sensor array is referred to herein as an “object scan line” or simply “scan line.” For descriptive purposes, a scanned object is considered to have a series of fixed adjacently positioned scan lines. Further, scanners are typically operated at a scan line sweep rate such that one scan line width is traversed during each sampling interval.
Differentiating from scanners employing CCDs, a contact image sensor (CIS) and CIS drive roller are commonly employed in document fed scanners for imaging the medium being passed (fed) through the scanner. The CIS is spring loaded against the drive roller and forms a nip therebetween. The medium being scanned is presented for scanning at the nip and is pulled past the CIS by the drive roller. The CIS typically includes a glass plate adjacent the roller (forming the nip), an array of light sources, such as light emitting diodes (LEDs), directed at the nip, an array of self-focusing lenses (cylindrical microlenses) that direct and focus the light from the light sources as reflected off the medium (or roller if no medium is present), and an array of photo sensors adjacent the self-focusing lenses for converting the light passed through the lenses to electrical signals for processing of the image generated. An advantage of the CIS is that it is less susceptible to having foreign particles (e.g., dust) settle on the CIS optics which could degrade the scanned image quality. A CIS is less susceptible to foreign particles because it has fewer reflecting optics, relative to CCD scanner devices, for focusing the light. Another advantage of the CIS is its small size due to its optical configuration.
It is known to provide a single plate flatbed scanner including an automatic document feeder which automatically feeds documents page by page. Each document fed into the ADF is conveyed to a scanning point or portion of the flat plate where the document is scanned by an image sensor and then the document is conveyed to a point outside the ADF, such as a document output tray. Typically, the image sensor remains fixed at the scanning point “reading” or scanning the image as the document is conveyed past the scanning point by the ADF. Another feature of the flatbed scanner allows a user to manually place or position an original document on the flat plate to be scanned. The document lays flat on and covers a portion of the flat plate while the image scanner is moved under the plate the length (or width) of the document to read or scan the document. In many flatbed scanners, the scanning point or portion of the flat plate used to scan a document provided by the ADF is separate and distinct from the portion of the flat plate utilized to scan a document manually positioned on the plate.
In some flatbed scanners, in order to reduce the size of the flat plate (and the overall size of the scanner), it is also known to utilize a portion of the flat plate for the scanning point for documents fed by an ADF (“ADF scan window”) which also forms a part of the flat plate portion for scanning documents manually positioned on the plate. However, a document manually placed on the plate will typically cover the entire plate including the ADF scan window. Thus, if a manually-placed document has been inadvertently left on the flat plate when a user attempts to scan a document using the ADF, the ADF scan window will be blocked, i.e., covered, and the ADF fed document will not be scanned. For this reason, many scanners, especially those used in multi-function devices, will employ a sensor to detect opening of the flat plate lid or cover.
Automatic document feeders typically also utilize sensors for detecting a leading edge of a document as it is withdrawn from an input or supply tray and fed into the scanner. From the point in time that the leading edge is detected, the amount of time required to convey the leading edge to the imaging sensor is monitored so that the imaging sensor may initiate actual imaging (scanning) at the precise time when the leading edge of the document reaches the imaging sensor. This amount of time will be more or less depending on the relative location of the sensor, or sensors, in the ADF document feed path.
Thus, a flatbed scanner employing an ADF may have at least two sensors, one to detect a document leading edge and one to detect the opening of the flat plate lid or cover. In order to reduce cost and component numbers, what is needed is a way to eliminate one or more of the presently used sensors yet maintain the required functionality.